


The Most Primitive Sense

by esterbrook



Category: Sherlock (TV)
Genre: 5+1 Things, For Science!, M/M, Scents & Smells
Language: English
Status: Completed
Published: 2013-02-02
Updated: 2013-02-02
Packaged: 2017-11-27 21:23:52
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,864
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/666645
Author URL: https://archiveofourown.org/users/esterbrook/pseuds/esterbrook
Summary: <blockquote class="userstuff">
              <p>a/k/a "Five times Sherlock studied John's scent, and one time he applied what he learned."</p>
            </blockquote>





	The Most Primitive Sense

**Author's Note:**

> Much appreciation to turifer and teahigh for beta duties.

 

~One~  
  
Sherlock leans forward in his armchair and sniffs. A moment later he stands up and does it again, first bending over to huff at the crown of John's head, then swooping down until his breath stirs the patch of greying hairs at John's left temple.  
  
"Oi!" John flinches and shoves at Sherlock's chest to push him back a step. Life with a brilliant madman has inured him to the unexpected, and this, to be sure, barely registers as odd on the Sherlock scale, but -- "Personal space, Sherlock," he protests. "What are you doing?"  
  
The word "obvious" seems to hang in the air as Sherlock sinks back into his chair. "You cleaned your gun today."    
  
John scrubs an abstracted hand across the back of his neck and reaches for his mug. "How could you tell?"  
  
"Because you showered last night before bed."  
  
"Go on, then," John allows. "Put it together for me."  
  
"You prefer to wash your hair in the morning. When you don't, you run your hands through it all day. The left side of your head is absolutely redolent of your favourite gun oil. Therefore..." He stops with a triumphant gesture.  
  
"And you are absolutely ridiculous," John informs him, laughing.  
  
Sherlock doesn't even try to suppress his answering smirk. "Says the man who orders his hair products from Sportsman Gun Centre."  
  
Later, as John is washing dishes, Sherlock ambles up beside him. "May I?" he asks, but it's _pro forma_. The long fingers are already wrapping around John's hand, lifting it out of the water and turning it wrist-up so Sherlock can inhale as if the dripping suds were fine perfume. By the time John shakes off the surprise and the grasp, Sherlock is halfway across the room again, muttering something about skin oils and surfactants.  
  
  
~Two~  
  
This continues at seemingly random moments -- sharing a cab, standing around a crime scene, sitting in Lestrade's office, digging through the contents of an abandoned storage locker. Sometimes Sherlock leans in for a quick, subtle sniff. Sometimes it's a deep inhalation. Once or twice it's an apparently involuntary snort, one loud enough to attract stares and offers of tissues.  
  
John assumes it has something to do with a case right up until the day he comes home from a trip to the pub and finds Sherlock in his bedroom -- standing in front of his open closet, to be precise. John stops in the doorway and watches, perplexed, as Sherlock methodically removes a shirt, holds it to his face for a few seconds, and jots something in his pocket notebook before replacing the hanger and moving on to the next.  
  
An ordinary flatmate would have the grace to look embarrassed at being caught doing something so inappropriate. Sherlock, naturally, doesn't even look up. "Dax or Bold?" he says, lifting John's favorite red button-down to bury his nose in the collar.  
  
"Whatever was on special last week," John replies automatically. Then his brain kicks in and registers what Sherlock is doing. "Wait. What?"  
  
"If you don't use the same washing powder all the time, how am I meant to identify clothing that belongs to you?"  
  
John feels -- by no means for the first time -- like he's walked into the middle of someone else's conversation. "I'm sorry, why would you need to identify one of my shirts based on the washing powder I'm using?"  
  
"It's not about the shirt." Sherlock finally meets his eyes, somehow both determined and defensive. "I want to be able to identify you by scent, and obviously, that needs to include whatever you're wearing."  
  
John grasps for an appropriate response. None is forthcoming, because really, what's appropriate when his lunatic best friend is taking an olfactory tour of his wardrobe? "And the reason for this is what, exactly?" he finally asks when no other question comes to mind.  
  
"It occurred to me that it could be useful. For example, if we were blindfolded and gagged and I needed to know you were nearby without alerting our captors -- "  
  
"I'd ask how likely that is to happen, except we both know it probably will at some point."     
  
" -- and you don't always smell the same," Sherlock rattles on. "You change washing powder or shampoo from time to time, or wear aftershave, or come back from the pub smelling of beer and crisps." He flaps a shirtsleeve with alacrity. "There are practically infinite combinations. I need to determine the most common individual components so I can establish a baseline."  
  
It makes sense, at least in their weird life. John embraces the inevitable and says, "I'll just leave off the aftershave, then, shall I?"  
  
"No, no," Sherlock says, looking as surprised and gratified as he did the first time John called him amazing instead of telling him to piss off. "Keep behaving as you ordinarily would. I'll make a spreadsheet."  
  
  
~Three~  
  
John remains unconvinced that the exercise is useful, but he can't deny that it's interesting, if only as a demonstration of Sherlock's sensory acuity. On ordinary days (which is to say, days that involve more sitting than running), the spreadsheet shows a combination of John's usual grooming products, laundry soap, tea, and whatever he ate the night before. On days he's picked up locum work, he evidently comes home smelling of antiseptic soap and exam gloves, with the occasional sour hint of vomit. An active case is fresh sweat, stale coffee, biro ink, and a whiff of cloying sweetness from the air fresheners dangling in every cab.  
  
As the experiment progresses, John begins to pay closer attention to the scents of the world around him. He notices the yeasty warmth billowing out of the bagel shop near his barber; the hairspray clinging to the woman next to him in the Tesco queue; the sweet, astringent citrus of the posh shaving soap Sherlock started using after -- well, they've agreed to call it his "travels" and leave it at that. He pays closer attention one afternoon when Sherlock tries to explain the conclusions he's drawn from the stench of the garbage in the skip they're hiding behind. He considers buying a new brand of shower gel at Boots just to find out what Sherlock might deduce from the change.  
  
Sherlock is, of course, right when he asserts that the sense of smell can be a powerful deductive tool; John still smirks whenever he sees an advert for deodorant "for men." Still, it's always impressive when he comes home from an evening at the pub and Sherlock announces -- without rising from the couch or even opening his eyes -- what John drank, whom he was with, and whether he managed to flirt anyone out of her phone number.  
  
One such pub night finds him coming home later than usual, uncharacteristically giddy with the aftereffects of too little sleep, too many pints, and a sloppy but enthusiastic snog in a dark corner. He's going to fall into bed and sleep, and that will be fucking glorious. But first he's going to indulge in a quick wank to the thought of...Amanda? Miranda? She'd scrawled her name on a napkin with her number and tucked it into his back pocket as he left. He could have gone home with her instead, except that he and Sherlock are taking the first  train to St. Albans, and Sherlock texted him three times in the last hour, and -- oh, god, Sherlock is going to do a smell check as soon as he walks in, isn't he?  
  
John doesn't need to hear any commentary right now about how he's still tipsy and a bit aroused; he's well aware of both of those things already, thank you very much. Deciding to bypass the living room entirely, he fires off a quick text on his way upstairs to tell Sherlock that he's home and going straight to bed.  
  
"Oh, hello," he sighs, less surprised than resigned, when he finds the man fidgeting expectantly on the edge of his bed. He supposes he could find it invasive, but if he minded Sherlock being Sherlock, he'd have moved out years ago. He unbuttons his cuffs, pulls his shirt off over his head, and chucks it into his friend's lap. "Do your worst, but make it march. I'm already asleep. I just haven't stopped moving yet."  
  
Sherlock takes one whiff and narrows his eyes. "Really, John, a woman who wears heavy floral perfume for a night at the pub?" Rising to stalk across the room, he circles once before ducking his head and shoving his nose nearly into John's neck. "And she was eating those prawn-flavoured crisps you like so much. I can smell them on you -- " He taps at what John realizes must be a love bite just above his collarbone. " -- right here. Where she put her mouth."  
  
John twitches at the pleasant ache of the long, cool finger on the bruise before shrugging the touch away. "And I could have had that smell on other parts of my anatomy, too," he says, smirking at the grimace he gets in response. "But instead I came home so we can catch our train in the morning. Which will only happen if you let me sleep now. So are we done for the night?"  
  
"I suppose," Sherlock grumbles, adding, "Belgian wheat beer?" John's nod of agreement gets a flicker of a smile. "Excellent, that's an entirely new data point. Good night, John."  
  
John shuts the door and waits until he hears the faint clatter of labware in the kitchen before stripping down to his pants and climbing under the covers. As tired as he is, a tiny ember of his earlier arousal is still glowing; he stokes it with memories of what's-her-name nipping at his neck, then fans it to a low flame by imagining her ice-blue eyes looking up at him through her long dark fringe as his prick slides between her plush lips. Eventually he shivers out a desultory climax. He cleans up afterwards with his discarded pants, lobs them in the general direction of his laundry basket, and plummets into sleep.  
  
The next morning, a hand shakes him awake while a voice says something urgent about the time. John's eyes and brain may be blurry with interrupted sleep, but he's not so blind or befuddled that he can't notice it's still dark. According to his alarm clock, he doesn't need to get out of bed for another hour.  
  
"Too early, you tosser," he growls, swinging a pillow squarely at the face bent over him. Sherlock pulls the pillow from his hands with an expression that John translates all too readily as "plans have changed." Ten minutes later, he's stepping out of the shower just as Sherlock opens the bathroom door and tosses in a clean shirt and last night's jeans.  
  
"What, you're my valet now?" he calls out.  
  
"Just hurry up," comes the reply from the other side of the already closing door.  
  
They hurtle onto the platform at St. Pancras just in time to catch their suspect disembarking. "It was the uniform," Sherlock explains as they march the defiant woman into a vacant office and lock her to the desk with yet another pair of handcuffs pilfered from Lestrade. "There's no reason for a conductor to smell of fish and chips at this hour of the morning. Obviously, she was wearing the same trousers she wore the night before."  
  
"Oh, obviously," John echoes, amused.  
  
Sherlock points out that John, too, is wearing last night's trousers, then demands them for some sort of test. There aren't many things John Watson won't do for Sherlock Holmes, but unless it's a matter of life or death, stripping off in the middle of a train station at the start of the morning commute is one of them. Sherlock, to his credit, says it can wait until they get home -- but as soon as the door to the flat shuts behind them, he points an imperious finger. John rolls his eyes and unzips.  
  
His favourite jeans reappear a few days later, freshly laundered and folded with mathematical precision. All that remains of the napkin with what's-her-name's number is a rock-hard lump of pulped paper in the hip pocket. John briefly curses his carelessness, but as Sherlock tartly reminds him, it isn't as if he's never going back to the pub. And when he finds a pair of his pants folded beneath the jeans, he allows himself a moment of smug triumph. Sacrificing a phone number, he thinks, is well worth the novelty of having Sherlock do his laundry.  
  
  
~Four~  
  
John is crouched on his heels, back to the wall. At the moment, he rather wishes "the stink of fear" was just a poetic turn of phrase; the miasma of terror in the room is so thick, he suspects it would be visible if there was any light to see by. At least the darkness shields him from whomever just fired a single shot through the open doorway. He doesn't dare make enough sound to present a target, but he urgently needs to know that the moist, bubbling gasps off to his left are coming from the man they came to find and not the brilliant idiot who charged recklessly into a windowless room to find him.  
  
A sharp whiff of citrus makes him sag against the wall in instinctive relief at its familiarity. In the next moment, a hand grasps his wrist and lips shape his name almost soundlessly against his ear. He breathes in another reassuring lungful to confirm that Sherlock is still near and prepares himself for action.  
  
Later -- gunman disarmed, client retrieved and sent off by ambulance, forensics team combing the scene -- John says, "You were right, you know."  
  
"I generally am." Sherlock smiles at John's exasperated snort. "About what?"  
  
"I couldn't see or hear you, but I knew you had to be right next to me because I could suddenly smell -- you. It. That shaving soap you like."  
  
"Of course. How do you think I found you? I followed my nose. Even in that fetid hole, you were unmistakable."  
  
John says something about the experiment being a success. "Of course it was," Sherlock says before pointing to Lestrade, who's turned his back to them. "Come on, John, now's our chance to escape. I have better things to do tonight than paperwork." And he's off in a clatter and flap, John as ever just two steps behind.  
  
A few days later, Sherlock stops John at their front door with a hand to the chest, closes his eyes, and inhales before charging out onto the street to flag a cab.  
  
"What was that all about?" John asks as he follows Sherlock into the back seat. "Thought you'd proved your hypothesis."  
  
Given their recent experience, Sherlock explains, he's decided that he needs to update his mental warehouse of data about John -- what he's wearing, what he's carrying, and, yes, how he smells -- every time they leave the flat for a case. "I want everything I know about you to be as up-to-the-minute as possible, in case I need that information in a hurry," he says. He leans fractionally closer, frowns, and blurts out, "Did Mrs Hudson bring us some of her sticky buns? I hope you saved one for me."  
  
John laughs and admits he accidentally bought cinnamon toothpaste. Sherlock snarls in irritation -- there's always something -- and demands, "Breathe in my face," so John does, drawing out the exhalation as long as possible while Sherlock eyes his half-open lips.  
  
  
~Five~  
  
The experiment may be a success, but it turns out to be far from over. Having established a baseline, Sherlock apparently wants to minimize the variables. Oh, he hasn't asked John to limit himself to one type of tea, and John emphatically vetoed the the suggestion that he stop taking the Tube entirely when they aren't on a case. ("I am not blowing my budget on cabs just to keep from offending your delicate nostrils," he'd scoffed.) But whatever Sherlock may say, John is no fool. When his flatmate -- who keeps enough caustic chemicals on hand to finance a dermatologist's yacht -- spends a full week insisting that their towels are giving him a rash, then stocks the flat with a year's supply of detergent for people with extra-sensitive skin, the word "unscented" on the label doesn't escape John's notice.  
  
"Thought you said you could find me by my washing powder," he teases as he prepares to lug his laundry downstairs. Sherlock rolls his eyes and asks if he's considered how many people use the most popular supermarket brands and how much more efficient it is to control for that.  
  
By the time John returns from putting in the first load, Sherlock is volleying texts at Lestrade. That turns into an increasingly caustic monologue about the idiocy of Lestrade, New Scotland Yard in general, England's criminals, and, indeed, the entirety of the human race. "It's going to be one of those days, is it?" John finally comments. Sherlock hurls himself onto the couch and snaps something about the horribly distracting thunk and clatter of the washing machine, two flights below. John opts for a tactical retreat to wait out the spin cycle at Speedy's.  
  
When he returns to the flat, all is silent. He expects to find Sherlock still on the couch, either deep in nicotine-patch-enhanced thought or curled up in full sulk, but the room is empty. He heads for the bathroom for a necessary break only to find Sherlock already in occupation, rubbing his face vigorously with John's bath towel.  
  
"Oh, there you are," John says. "Did you solve Lestrade's case?"  
  
"Noooo..." comes a muffled reply, but suddenly Sherlock pulls the towel away to reveal the startled yet knowing expression John privately calls "deduction face."  
  
"Oh! The uncle is only related by marriage!"  
  
John wants to hear the explanation, he always does -- but at the moment, he has a higher priority, so he shoos Sherlock out mid-sentence. He doesn't notice until later, when he needs the towel, that Sherlock has taken it with him. All their other towels are, of course, still in the dryer.  
  
"You must have grown up in a very posh barn," he grumbles when he emerges, wiping his damp hands on his trousers. "Don't you know to leave one towel in the damn loo no matter what?"  
  
Sherlock, in the kitchen, is still clutching the towel in one hand. He looks down at it as if it had jumped into his grasp on its own before dropping it on the table and grabbing John by the arm. "Never mind that, John," he exclaims as he hustles them out the door. "Come on, we have a con man to catch!"  
  
  
~And One~  
  
Fairy lights twinkle around the window and twine around the skull's brow like a crown. The flat is fragrant with mulled wine and Mrs Hudson's spice cake, cedar garlands and beeswax candles. The first holiday party since Sherlock's return has wound to a successful close, and by "successful" John means nothing exploded and no one stomped out in tears. John's going to consider it a new tradition.  
  
The tradition of Sherlock slouching in his armchair next to the fire while John tidies up is, naturally, already well-established. John stacks the last of the dirty glasses in the sink and slides into his own chair. "You're helping me wash up in the morning, you lazy twat," he says, nudging Sherlock's foot with his toes. "Consider it a Christmas gift." Sherlock makes a quiet sound in the back of his throat that John chooses to interpret as agreement.  
  
It's warm, they've both had a few drinks, and the crackling fire is the loudest sound in the room. John shuts his eyes and wonders, with a contented sigh, if they're actually going to fall asleep in their chairs like old men. Not that he would mind. He doesn't think of old age often, but if they survive that long, he supposes that sitting by the fire after a long, good day would be a decent enough metaphor.  
  
"Smell is the most primitive sense," Sherlock abruptly says in a low voice, as if they'd been talking about it all along. "It's located in one of the oldest parts of the brain, the limbic system, the part that controls emotions and memory. Smells can affect concentration, mood, appetite, even body temperature."  
  
"Introductory biology, that," John acknowledges.  
  
"An odor can trigger intense emotions and memories before the brain even identifies it," Sherlock continues. He sounds annoyed. "Sometimes I need a full second to realize what I'm reacting to."  
  
The last few words are louder, closer, more petulant. John opens his eyes to Sherlock bending over him, face just inches from his own. He inhales sharply, winding up to protest, but the air leaves his mouth in a startled squeak as Sherlock drops to his knees and presses his nose into the hair at John's temple.  
  
"I tried to isolate what it was," Sherlock mutters. "I eliminated everything I could, hoping I could at least minimize the effect, but it's still there."  
  
"What -- "  
  
The breathy noise Sherlock makes could be anywhere on the spectrum between profound satisfaction and aching impatience. "The way you _smell_ , John."  
  
John is astonished by an unexpected urge to cup his hand around the back of Sherlock's head to keep him from pulling away. This is certainly not the first time he's felt drawn to the man, but it is the first time he's recognized it for what it is. He shudders at the strength of his instinct to turn his face against Sherlock's cheek, into those dark curls, and breathe him in -- shaving soap and woodsmoke and whatever it is beneath them making his pulse hammer like they're running together through the London streets.  
  
"That's why I borrow your clothes and towels," Sherlock continues as he traces the rim of John's ear with the tip of his nose. "They help me think. Safer and less expensive than cocaine, easier to come by -- and I can put them back in the laundry hamper when they stop smelling of you."  
  
"My -- my clothes and towels?"  
  
"Things that have absorbed your sweat," Sherlock says, voice less a sound than a vibration in the hollow behind John's jaw. "Things that have rubbed against your skin."  
  
John feels his world rearrange itself in the same way it did the day he first sat in the back seat of a taxi while a man he barely knew told him about himself, or the day he came home to find his best friend's ghost in his living room. He slides one hand along Sherlock's bicep, around the curve of his shoulder, up into the curls edging the nape of his neck. "Is this helping you think now?" he asks. Sherlock's head moves beneath his fingers, shifting in a slight nod. "Is it for a case?" Warm lips breathe out an affirmative against his neck, sending a tremor from the base of John's skull to the pit of his stomach. "What case?"  
  
"This," Sherlock says, and his hand comes up to grab John's chin just as John's fingers tug lightly at Sherlock's hair to tilt back his head. Kneeling in front of John's chair, Sherlock is precisely the right height to tip their foreheads together for a moment of sharing the same wine-and-spice-scented breath. John's stomach flips with the terrified exhilaration he felt the first time he applied a tourniquet during a firefight. Then Sherlock presses forward and John instinctively moves to meet him.  
  
This is not a kiss. This is an explosion blasting him into splinters. This is a solution melting him down to his component elements. This is incinerating, obliterating, one of Sherlock's experiments embodied in lips and teeth and tangling tongues.  
  
When he rips away his mouth to gasp for air, he finds his hands wound into Sherlock's hair as though it's the only thing saving him from destruction. Sherlock's hands, for their own part, are gripping John's shoulders so tightly he suspects he'll have thumb-sized bruises in the dip just above his collarbone. They stare at each other, wide-eyed and shaking as if they've just cheated death. It feels familiar. It feels fantastic.  
  
John manages a cautious smile at the man kneeling between his splayed knees. "Another experiment?"  
  
Sherlock bites his lip. "Still the same experiment," he says. "There's still so much to know. So to speak." He watches his own hands as he slides them down to John's hips and then around to the button of his jeans, then looks up from beneath disheveled curls and says, "Let me."  
  
And oh, John thinks with a shiver, he's just two steps behind Sherlock as usual. Maybe only one, albeit a big step, one that could upend life in 221B permanently. But where Sherlock leads, he's determined to follow. He drops his hands to the arms of his chair, takes a deep breath, and nods.  
  
"Fucking hell," he hisses as Sherlock tugs open his flies and bends down to press his nose into the crease of John's groin.  
  
"Oh, this is what I needed." Sherlock's voice is eager and curious. He noses at the thin cotton of John's pants. "Not diluted. Not second-hand."  
  
"Don't think you can just do this at crime scenes any time you're having trouble concentrating." John tries to keep his voice light, even as his entire body trembles.  
  
"Scent is an intense trigger, John," Sherlock says. "Evocative. Powerful." He inhales through both his nose and his mouth like John is a glass of wine he's tasting, then works down the waistband of John's pants.  
  
"Jesus, Sherlock." John's hips rock up involuntarily. "What are you -- " The rest of his question dissolves into a rising whine as a determined tongue swirls a spiral pattern around the head of his rapidly hardening cock before retreating.  
  
John lifts his head to lock eyes with a version of Sherlock he's never met before: cheeks flushed, breath unsteady, shirt coming untucked from half-undone and thoroughly tented trousers. He wants this, he realizes -- not just because he's in the habit of doing what Sherlock wants, but because what Sherlock wants is usually what they both need. With that thought, he slides out of the chair to kneel facing Sherlock and shoves his pants down his thighs. Sherlock raises his eyebrows in genuine surprise, then mirrors him, twitching and gasping as their cocks bob and brush together. When he wraps his fingers around John's fingers and guides them to encircle both erections at once, John drops his forehead to Sherlock's shoulder.  
  
"When -- " he breathes, knowing Sherlock will understand what he's asking: _When did you start to want this?_  
  
"The night before we were planning to go to St. Albans," Sherlock replies. "You came home from the pub, and I knew you were -- " One long, slow stroke of their joined hands briefly silences him. "I mean, I could tell that someone had -- aroused you. And I -- ."  
  
"You nicked my jeans the next day," John rasps.  
  
"Not just your jeans. Your pants, too. Kept those for days."  
  
The image explodes fully formed into John's mind: Sherlock grabbing a shirt from John's wardrobe and the jeans at the end of his bed while he showered, noticing the crumpled, obviously well-used pants in the laundry basket, pausing in his rush long enough to pilfer them for later…examination. "Oh, fuck, Sherlock," he growls, bucking harder into their shared grip.  
  
Sherlock does the same, increasing the speed and pressure of their fingers. "You always smell so good. Like home." His voice is breaking, hitching in time with the rhythm of their hips, the slide of their cocks against each other. "And I don't. Want. To share. My home. With. Anyone. Else."  
  
The last word wavers into a drawn-out hiss as Sherlock grinds against him urgently, wordlessly. The sound hammers at the base of his spine, jolts through his groin, and rips a blissful obscenity from his mouth as he comes sudden and fast and almost painfully hard. He manages to keep his hand moving, warm and wet, long enough for Sherlock to gasp his name and shudder against him in turn.  
  
He has no idea how long they lean against each other afterwards, or how they end up lying naked on the carpet, where Sherlock is now examining him with the same meticulous attention he applies to a crime scene. "So," John eventually says with the carefree lassitude of the well-shagged, "the flat smells like tea and my shampoo?"  
  
"No," Sherlock replies. "I didn't say home smells like you." He slides up to lie against John's side, cheek against his good shoulder, and tucks his nose back into the hollow behind John's jaw as he adds, "I said you smell like home."  
  
John turns his head until he can feel curls tickling his nose. He smells the unmistakeable fresh scent of sweaty, enthusiastic sex, but it doesn't drown out the citrus and smoke and old books, the spices and chemicals and blood and takeaway curry, all the odors that conjure up 221B and the life they live there. It somehow simply enhances them.  
  
"That's funny," he murmurs contentedly into Sherlock's hair. "So do you."  



End file.
